I heard you mention that you wanted to explore another part of the Caribbean? My wife and I have been on both the western and southern caribbean iteneraries and I must say we prefer the Southern Caribbean on the Adventure of the Seas out of San Juan. The airfare is a little more expensive, however, the ports of call (Aruba, Curacao, St. Maarten and St. Thomas) are worth the extra expense. The Adventure, of course, is the same size as Mariner.
I'm sure you'll have fun with whatever you decide.
We have been on all three of those lines (within the past year)as well as 8 other cruise lines (guess we like to cruise). All 3 of those lines are comparable and each has their pros and cons. I would probably recommend Princess or RCI but would be hesitant to suggest that a couple your age go on HA since that line tends to attract an older crowd (me). That being said, the Noordam is an absolutely gorgeous ship so perhaps that might be the exception. My suggestion would be that you take a good look at all the available itineraries and prices and make that your primary consideration when choosing your cruise.
Hi jmcs, the Dive-In program allows you to snorkel in every port on that particular itinerary. We signed up for the early excursions. Any port we were in, we were able to be in the first group off the ship. They provided snorkeling gear that you could keep with you the entire cruise. We later bought our own. The one time fee included all of the transportation and snorkeling in each port. I think it was $250/pp, but I could be wrong about that. It did work out saving us money. By doing the early excursions, we had time to visit the port in the afternoons. My favorite snorkels in the Caribbean are: 1. Champagne Reef-Dominica, 2. Flamingo Bay-Grenada, 3. Isla Catalina-Dominican Republic, 4. Trunk Bay-St. John, 5. Norman's Island Bat Cave-Tortola, 6. Xel-ha-Cozumel, 7. The Pitons-St. Lucia, 8. Tiami Sail/Snorkel-Barbados, 9. Buck Island-St. Thomas, 10. Sapphire Beach-St. Thomas. I'm sure there are others, but these stand out and are pretty much in the order of preferance. Hope this helps!
I'll weigh in on this. First, I'm an agent and a cruiser. HAL, as stated previously is geared and marketed toward a more senior market. If the pricing is also out of line scratch it off your list.
Princess and RCCL have much in common, between the two it comes down to itinerary more than anything else. Both have great loyalty programs so if you try them both and have a favorite stick with that line and you'll love the perks you begin accruing. RCI platinum status begins after only 5 sailings. PCL lets you purchase FCC's (future cruise credits) from your first time aboard their ship. RCI, you can also book a future cruise onboard. Both of these will get you some onboard credits with your next booking and a few other perks. You won't go wrong with either line.
NCL is a completely different line in almost every way. Dining, dress code, etc. are different from the rest of the industry. They call it freestyle cruising. No assigned times, eat when you want and where you want. I have a short one for the inaguural sailing of NCL Gem booked out of NYC in December. They get a lot of bad press (they earned some of it in the past and still in their Hawaii market) but much of it unwarranted, a lot like Carnival. It's chic to say about the cruiselines that focus on the value end of the market that "I'd never cruise with them" or "You get what you pay for". If you sail on one of NCL's newer ships I'd be willing to bet you'd have a great time. They have among the most loyal followings of any cruiseline. People either love or hate freestyle. Very few like me who like both.
I sailed RCCL, Adventure of the saes last month and will agree with Wheels that it's one of the best caribbean itins out there and a sister to the Mariner. Same feature, size, design, just a little different decor but not much different.
I know all this is not a great help since in my opinion there is not really a bad choice among your list. Look at the itineraries and go have a great cruise!